/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.transforms;



import com.bff.gaia.unified.sdk.annotations.Internal;

import com.bff.gaia.unified.sdk.coders.ByteArrayCoder;

import com.bff.gaia.unified.sdk.io.Read;

import com.bff.gaia.unified.sdk.transforms.windowing.GlobalWindow;

import com.bff.gaia.unified.sdk.values.PBegin;

import com.bff.gaia.unified.sdk.values.PCollection;

import com.bff.gaia.unified.sdk.values.WindowingStrategy;



/**

 * <b><i>For internal use only; no backwards-compatibility guarantees.</i></b>

 *

 * <p>A {@link PTransform} which produces a single empty byte array at the minimum timestamp in the

 * {@link GlobalWindow}.

 *

 * <p>Users should instead use {@link Create} or another {@link Read} transform to begin consuming

 * elements.

 */

@Internal

public class Impulse extends PTransform<PBegin, PCollection<byte[]>> {

  /** Create a new {@link Impulse} {@link PTransform}. */

  public static Impulse create() {

    return new Impulse();

  }



  private Impulse() {}



  @Override

  public PCollection<byte[]> expand(PBegin input) {

    return PCollection.createPrimitiveOutputInternal(

        input.getPipeline(),

        WindowingStrategy.globalDefault(),

        PCollection.IsBounded.BOUNDED,

        ByteArrayCoder.of());

  }

}